A circuit capable of converting an available ac voltage to a dc voltage is known as a dc power supply. The dc power supply has a rectifier type circuitry. One of the drawbacks in a conventional rectifier circuitry is that the converted dc voltage includes some ac ripple voltages, thereby hampering the rectifier's ability to deliver a pure dc voltage. In addition, the converted dc voltage may be reduced as more load currents are drawn, thereby causing an unevenness in the power supply voltage. In order to minimize such variations, a linear regulator power supply is normally used. The linear regulator power supply conventionally includes an operational amplifier (hereinafter referred to as an "op amp").
During a normal operation of the linear regulator power supply, a short-circuiting may occur in its dependent load resulting in an abrupt overcurrent passing therethrough, which may cause a breakage thereof.
In order to provide a protection against such an occurrence, a fuse system is normally used in the linear regulator power supply to decouple the overcurrent. However, one of the major short-comings in this approach is that the fuse must be exchanged or reinstated each time the short-circuiting occurs.